The DPMS LR line has a different pattern barrel nut. I used a Tacpo wrench to remove the factory barrel nut but it only engaged two of the three points, the third hit the treads. I couldn't install the SASS handguard barrel nut without this specific wrench

I dry fit the hand guard and can get it fairly tight with the Tapco wrench but as much as you spend on the guards I don't want to damage anything trying to get extra torque, so I would really rather have the right tool when making the final fit